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Lightweight reinforced concrete (LWC) is widely used in various reinforced concrete (RC) applications, such as its use in diverse types of reinforced concrete slabs. The aim of this study is to analyze the behavior of reinforced foam concrete slabs (flat slab type) that are exposed to fire conditions under the influence of eccentric loads as well as concentric loads. This analysis has been done using the finite element method by a (ANSYS) software program. The validity of the adopted models was verified through comparison with a previous experimental study. The studied specimens were eleven reinforced concrete flat slabs with a thickness of 150 mm. The lightweight polystyrene foam concrete was used in these specimens with a density of 1820 kg/m3. The results showed that the fire effect lead to a decrease in the maximum carrying load of foam concrete slabs by 25%. Also, by comparing the finite element results with the selected experimental study, the results showed a great agreement with the analytical study used in this research.

The construction industry is one of the most complex industries, and it involves numerous change orders. Change orders often occur in all or some phases of industrial construction work and have a significant impact on the success of the project, its on-time completion, or ultimately, an increase in the estimated cost of the project. Change orders are one of the most frequently common problems facing construction projects in Saudi Arabia. The purpose of this study is to examine the impacts of change orders on construction projects in Saudi Arabia and identify preventive solutions to mitigate these impacts. To achieve this objective, the effects of change orders on construction projects in general were identified through a comprehensive literature review. Then, an analytical study was conducted on five construction projects in diverse universities in Saudi Arabia. Following that, interviews were conducted with some experts in these projects. Finally, a survey was conducted by distributing questionnaires to the parties involved in the projects, and the responses were analyzed by using the relative index method. A triangulation technique involving collecting data from the analytical study, the interviews, and the survey was used to improve the validity of the findings. The results showed that the major impacts of change orders on construction projects in Saudi Arabia were on meeting the needs of the project, disputes among parties of the project, and the development of project specifications. A set of preventive solutions were suggested to mitigate these impacts, such as having all parties study the project and coordinate between them before starting the project and hiring a specialized consultant with experience in similar projects.

The aim of this paper is to assess the structural behavior of hybrid thin-walled beams which were fabricated using laminated carbon fiber reinforced polymer (CFRP). Seven hybrid (CFRP) I-beams were fabricated, instrumented, then have been tested under monotonic four-point loading in order to evaluate their behavior up to failure. In constructing the I-beam specimens which were evaluated in this study, plywood core was implemented on both the web and flanges. Several important parameters were conducted in this study considering changing both of the ply orientations and stacking sequences of laminated fibers, also changing the shear span-to-depth ratio (a/d) of the specimens. The experimental results showed that stacking sequence is the most significant parameter that influences both flexural strength and stiffness of the hybrid beams. Also, the experimental results promoted the effectiveness of the core material for enhancing the flexure (bending) stiffness of beams. Then, these results were compared with a previous simulated study which used the finite element modeling to model the beams. Also, in order to evaluate the efficiency of the CRFP beams, the results were compared to similar steel beams having the same dimensions of the CFRP beams. As compared to steel beams, the load carrying capacity of the laminated beams is being high compared with steel beams when taking into consideration their specific strength ratio.

Based on modified methods for the results of first-order analysis of RC columns, different codes approximate the second-order effects by using equations focusing on the maximum additional moment through the column height. These equations did not refer to the additional moments between the column and the connected beam, only the effect of the connected beams is taken into consideration by dealing with the effective length of the column, not the total length. Moreover, these equations did not take into account the second-order effect, which is caused by axial force and the inverse moments due to beam restriction for the column ends. This paper presents a new moment magnifiers matrix for the additional moments at the connection between braced columns and the connected beams as a simplified computation that can be used in the design procedure. That is through an equation based on transforming the original long column in second-order analysis to an equivalent isolated column. The equivalent column was represented as an element restricted with rotational spring support at its ends, and it is subjected to lateral distributed loads that have the same influence of the second-order effect on the induced additional moments in the long column. The suggested equivalent column can be used to form the additional bending moment diagram, also to compute the additional deformations as well. Numerous factors were analyzed linearly by using the presented new moment magnifiers matrix and finite element method, and the results proved the efficiency of the proposed model. Although the presented suggested model is based on the isolated analysis of the long column, the effect of the additional moments in the adjacent long column can be considered by presented two suggestions to improve the model. Also, development was proceeded on the model by modifying the flexural rigidity (EI) which is recommended in ACI to appropriate the time of failure. The additional moment values of the developed model were close to the values calculated by the ACI equation.